1. Field of the Invention
The present invention relates to an optical interrogation system and method capable of generating light beams that have desired optical properties which are directed towards a specimen array.
2. Description of Related Art
One of the most significant challenges for manufacturers of optical interrogation systems is to design an efficient and cost effective system that is capable of illuminating an array of specimens with light beams that have desired optical qualities like the proper spatial, angular, and power profiles. This problem becomes even more acute as the dimensions and the density of the array of specimens increase. In the past, optical interrogation systems have used lenslet arrays, fiber arrays, “flood illumination” and scanning methods to address this problem. Unfortunately, these systems are often costly to construct and difficult to use because it is hard to generate light beams that have the appropriate optical character and which align with all of the specimens. Another reason why it is difficult to design efficient and cost effective optical interrogation systems is because the specifications for the system design often have conflicting requirements. The following is a list of some of these different scanning and non-scanning applications and their associated requirements:                Application—high specimen density.                    The optical interrogation system will have to make many moves to scan the entire specimen array.            The optical interrogation system will have to incorporate a plurality of identical optical components which are precisely machined and positioned.                        Application—large specimen array area.                    The optical interrogation system should have a large scan range.            The optical interrogation system should be able to perform high-speed moves between specimens.                        Application—precise positioning and re-positioning of the light beam and/or specimen array.                    The optical interrogation system should have a small step size resolution.            The optical interrogation system should have precisely machined motion hardware and optics.            The optical interrogation system should have encoder feedback hardware.            The optical interrogation system should move slowly to allow precise alignment and re-alignment to each specimen.                        Application—maximum integration time at each specimen.                    The optical interrogation system should be able to maintain a light beam at each specimen location for long data integration periods.                        Application—rapid repetition of the scan of the specimen array.                    The optical interrogation system should be able to perform high-speed moves between specimens.            The optical interrogation system should have a short interrogation time at each specimen.                        Application—precisely controlled beam intensity, spatial profile, and angular profile characteristics at each specimen.                    The optical system requires many optical components with precise optical characteristics and positions.                        
One optical interrogation system that can generate multiple light beams while using few or no moving parts incorporates an array of optical components such as a lenslet or fiber array. However, these types of optical interrogation systems have several drawbacks. First, these systems require the use of a number of precisely positioned and designed optical elements in order to convey light beams to one or more lenslets, fibers, and/or specimens. Another drawback of these types of optical interrogation systems is that they require the use of additional components to ensure that the light beams have the appropriate optical power and intensity profile when they are introduced into each lenslet, fiber or specimen.
Another type of optical interrogation system could incorporate a device such as a beam expander that “flood illuminates” the specimen array. However, these types of optical interrogation systems have several drawbacks including (1) loss of optical power when light beams fall outside the lenslet elements, fibers or the specimen interrogation region; (2) increased measurement noise and error due to light beams that scatter from undesirable regions of the lenslet, fiber or specimen array; and (3) difficulty of ensuring the proper illumination including intensity, numerical aperture, etc. of all elements in the array of lenslets, fibers or specimens.
Yet another type of optical interrogation could rely on various scanning methods to illuminate the specimens. However, these scanning systems have several drawbacks because they require the use of precise alignment hardware and software and they do not allow for long integration times at each specimen. Accordingly, there is a need for a new optical interrogation system that addresses the aforementioned shortcomings and other shortcomings in the traditional optical interrogation systems. These needs and other needs are satisfied by the optical interrogation system and method of the present invention.